Ion guides, ion traps, ion stores and fragmentation devices are frequently used in mass spectrometers. These structures are used, for example, to transport ions between structures in the mass spectrometer, such as between a mass selection region and a time-of-flight region, or to temporarily store and/or fragment ions. This is generally achieved by use of a multipole device such as a quadrupole device (other multipole devices are possible, e.g. a hexapole device or an octapole device). As there is typically no analytical capability required of multipole devices, they are generally manufactured to looser tolerance requirements (i.e. lower accuracy) than devices used for mass analysis. Consequently, the manufacturing/assembly method used to form a multipole device should be chosen appropriately. For example, the use of high accuracy ceramics and ground electrodes would normally be considered inappropriate for manufacturing multipole devices, as these methods are more expensive and therefore normally reserved for components requiring high accuracy.
The present invention was devised by inventors searching for a simple method to manufacture a multipole device for use as an ion guide in a mass spectrometer.
Current standard methods for manufacturing multipole devices might employ metal electrodes supported by a plastic (or other insulating) support structure. These methods are generally adequate, although in some cases there is also a requirement to enclose the ion guide structure, e.g. for the purpose of providing a predetermined gas pressure profile in the multipole device. This is normally achieved by enclosing the multipole device in a can or tube.
The present inventors have observed that in the case where a multipole device has segmented electrodes that include many electrode segments (e.g. as might be needed when multiple DC electrodes are used to accelerate ions through a gas pressure), it can be complicated to apply different radiofrequency and DC voltages to the multiple electrodes segments, since multiple individual connections need to be made from voltage sources to the multiple electrode segments.
The present inventors believe it would be desirable to make multiple electrodes part of a single larger assembly to simplify alignment of adjacent electrodes relative to one-another.
U.S. Pat. No. 8,835,839B1 describes an ion manipulation method and device. The ion manipulation device described by U.S. Pat. No. 8,835,839B1 includes a pair of substantially parallel surfaces. An array of inner electrodes is contained within and extends substantially along the length of each parallel surface. The device includes a first outer array of electrodes and a second outer array of electrodes. Each outer array of electrodes is positioned on either side of the inner electrodes, and is contained within and extends substantially along the length of each parallel surface. A DC voltage is applied to the first and second outer array of electrodes. A RF voltage, with a superimposed electric field, is applied to the inner electrodes by applying the DC voltages to each electrode. Ions either move between the parallel surfaces within an ion confinement area or along paths in the direction of the electric field, or can be trapped in the ion confinement area. U.S. Pat. No. 8,835,839B1 indicates that the ion manipulation device can be fabricated and assembled using printed circuit board technology and interfaced with a mass spectrometer. The ion manipulation device is referred to as a Structure for Lossless Ion Manipulation (“SLIM”) device. A range of uses are proposed for this SLIM device.
WO2012/150351A1 discloses a device for charged particle transportation and manipulation. Embodiments provide a capability of combining positively and negatively charged particles in a single transported packet. Embodiments contain an aggregate of electrodes arranged to form a channel for transportation of charged particles, as well as a source of power supply that provides supply voltage to be applied to the electrodes, the voltage to ensure creation, inside the said channel, of a non-uniform high-frequency electric field, the pseudopotential of which field has one or more local extrema along the length of the channel used for charged particle transportation, at least, within a certain interval of time, whereas, at least one of the said extrema of the pseudopotential is transposed with time, at least within a certain interval of time, at least within a part of the length of the channel used for charged particle transportation.
In devising the present invention, the present inventors sought to design an ion manipulation device that would permit easy application of different voltages to multiple electrodes, that would provide a simple structure for relatively low manufacturing cost, and a structure that could optionally be enclosed, allowing the gas pressure within the ion manipulation device to be optionally controlled independently of a vacuum chamber optionally containing the device. Note that controlling the gas pressure within an ion manipulation device might be useful if the ion manipulation device is configured as a collision cell, which can be viewed as an area of a mass spectrometer where ions are fragmented by way of collisions with a high pressure background gas. Although given specific nomenclature, a collision cell can also be viewed as an ion guide with a high local gas pressure.
The present invention has been devised in light of the above considerations.